The present invention relates to data recorders and, more particularly, to digital data recorders adapted for remote access over dial-up telephone lines.
Since the earliest days of utilities providing energy in the form of gas and electricity, the consumption of energy has been metered at the user's location. Collecting the metered data has been done traditionally by a meter reader visiting the user's consumer's location at regular intervals to note the indication on an indicator such as, for example, dials or drums on an electro-mechanical register or an electronic display or digital readout. In one series of electric meters produced by the General Electric Company, readout accuracy and speed are enhanced by an optical readout device accessing the data through an optical port provided under the trademark Optocom.
The cost of electric energy is generally considered to consist of two parts: out-of-pocket costs and capital costs.
Out-of-pocket costs are those required for the generation and distribution of the electric energy. Such costs are fairly recovered by a charge based on the actual consumption of energy.
Capital costs are those that the utility must bear to be prepared to supply the total electricity needs of all of its consumers. It is well known that the consumption of electricity has diurnal, as well as seasonal, patterns. In hot summer weather, for example, it is well known that peak consumption is reached in some systems in the late afternoon as consumers return home and turn on their air conditioners. In winter, similar peaks arise from lighting loads synchronized by early darkness causing business and residential consumers to turn on lighting fixtures at about the same time. Business and industrial consumers produce consumption peaks from motor start-up loads and the energy consumption of air conditioning, lighting and other business and industrial uses.
The size and cost of a plant for generating and distributing electricity are determined by the peak load the plant must accommodate. Thus, the capital cost of building a generation and distribution facility is similarly governed by the peak load, rather than the average load.
Demand metering is concerned with the magnitudes of consumption peaks rather than with the times they occur. Conventional demand meters accumulate the amount of energy usage in each of a continuous sequence of demand intervals. At the end of each demand interval, the energy consumption in the interval is compared to a stored value representing the maximum demand in all previous demand intervals in a current period. If the demand in the just-ended demand interval exceeds the demand in the previous demand interval having highest demand, a new highest-demand is stored and the previous high demand is erased. When read out, the maximum demand is used to influence the rate at which the consumer's total electric energy consumption is billed for a period which may extend for a period as long as a year or more.
The familiar electric meter for residential consumers contains a mechanical register accumulating total energy usage in units of, for example, kilowatt hours. No distinction is made for the time during which the consumption occurs or for peaks in energy consumption, as in time-of-use and demand systems. The times (of day, week and year) during which consumption occurs is critical to time-of-use or demand metering.
Electronic demand and time-of-use register generally mimic the functions of their mechanical predecessors. Most electronic registers add display and analysis features not easily implemented in mechanical registers, but not of interest to the present invention.
Physical reading of registers in electric meters is a substantial burden on the utility providing the electric energy. It is thus desirable to provide means for the utility to read the consumption and time-dependent time-of-use and/or demand data from user's registers without requiring a personal visit by a meter reader.
One way to provide remote reading of a register includes a dedicated line such as, for example, a dedicated telephone line between a metering data center and a register in a consumer's facility. The metering data center is thereby enabled to query the condition of registers in the consumer's facility at will. From a practical standpoint, an energy consumer, absent a metering failure, requires a readout only at intervals of, for example, once a week or once a month. It is unlikely that a utility is cost justified in interrogating the registers of even a large energy consumer more frequently than once a day. Thus, the relatively high cost of a dedicated telephone line is difficult to justify, even in the case of a large energy consumer.
Another way to provide remote reading includes the use of a dial-up telephone line with an auto-dial, auto-answer MODEM (modulator-demodulator) at the user's location. The amount of data that must be transmitted at any time between a metering data center and an energy user fits well with the data transmission rates of which commercial MODEM devices are capable.
It is preferred that a data-communications system used with the present invention be able to share telephone facilities with other uses such as, for example, normal incoming or outgoing voice communication. Such sharing requires that the system be able to recognize that the telephone line is in use, and to delay demanding use of the telephone line until it is free. It is further desirable that means be provided to permit the data-communications system to be accessed by an incoming call. Such means may include, for example, an auto-answer function in which the system engages the incoming line after a predetermined number of rings have elapsed.
Whenever incoming telephone calls may access a data-communications system, the subject of data security arises. It is not wise, in a revenue-intensive system such as a metering data communications system, to permit unauthorized access to the data and, perhaps more importantly, it is crucial to prevent unauthorized tampering with the data or operating system. One method for avoiding unauthorized access to a data system includes the requirement that access to data requires input of a password. In the absence of the required password, access is denied. A password can consist of any combination of alphanumeric and punctuation characters receivable by a MODEM.
A further access-security method includes callback control, wherein access to the system requires that an incoming call begin with a predetermined user code, equivalent to a password, be transmitted by the station calling in. The data communications system then hangs up. If it received a correct user code, it calls a telephone number associated with the user code. Only then is communication established. Thus, in order to establish communications, an incoming caller must have the correct user code and access to the particular telephone dialed in response to the user code.
Numerous other security techniques including, for example, encryption, are well known to those skilled in the art and thus do not require further description.
Best advantage can be taken of access through a dial-up telephone line if the line can be used for other purposes when not needed by the data communications system. For example, the data communications system may be connected in parallel with the user's existing telephone line. Except for a few relatively short periods when the data communications system is in the process of communicating data with the metering data center, the user's line is undisturbed by the presence of the data communications system. Steps must be taken to prevent the data communications system from interfering with other uses and to prevent other uses from corrupting the transmitted data.
Besides a data-communications system, an electronic remote data recorder requires holding and recovery techniques to survive an intentional or unintentional power outage. Holding may be performed with battery backup for the most critical components and data. Recovery requires that recording resume without losing revenue data and with time-dependent functions updated according to actual clock time, regardless of the conditions that prevailed when the power loss occurred. In addition, means for programming the functions of the electronic remote data recorder, preferably over a telephone line, are desirable. An ability to reprogram remotely suggests that special security measures be provided to avoid unauthorized tampering with this function.